1. Field of the Invention
The present invention relates to a pivotal structure for an impeller shaft of a miniature heat dissipating fan
2. Description of the Related Art
Taiwan Utility Model Publication No. 355037, issued on Mar. 21, 1999 and entitled xe2x80x9cIMPROVED BEARING LUBRICATION FOR A BRUSHLESS D.C. FANxe2x80x9d, discloses an oil-pregnant bearing with a bore for receiving an axle, wherein a reservoir is defined in a middle portion of the bearing bore for receiving lubrication oil, and the pivotal seat of the fan housing includes a number of grooves for containing lubrication oil of the lubrication oil supply system.
It is, nevertheless, found that the bearing and the axle have a considerable contact surface area for rotation and thus have a larger frictional surface. Thus, noise tends to occur after a long-time use. In addition, the manufacture of the above-mentioned structure is troublesome and the cost therefor is high.
It is a primary object of the present invention to provide a pivotal structure for an impeller of a miniature heat dissipating fan in which the axle and the bearing member for supporting the axle have minimized contact surface area therebetween, thereby reducing the rotational noise and increasing the life for use.
It is a secondary object of the present invention to provide a pivotal structure for an impeller of a miniature heat dissipating fan in which the impeller can be easily assembled and the manufacture cost is reduced.
In accordance with the present invention, the axle and the bearing member for the axle have a minimized point contact therebetween. In addition, a balance plate is mounted below the ring magnet of the rotor. The balance plate and the ring magnet are positioned in a balanced manner and attract each other to thereby guarantee stable rotation of the impeller and minimized frictional contact between the axle and the bearing member.
Other objects, specific advantages, and novel features of the invention will become more apparent from the following detailed description and preferable embodiments when taken in conjunction with the accompanying drawings.